Structure and method for forming programmable high-k/metal gate memory device

ABSTRACT

A method of fabricating a memory device is provided that may begin with forming a layered gate stack overlying a semiconductor substrate and patterning a metal electrode layer stopping on the high-k gate dielectric layer of the layered gate stack to provide a first metal gate electrode and a second metal gate electrode on the semiconductor substrate. In a next process sequence, at least one spacer is formed on the first metal gate electrode overlying a portion of the high-k gate dielectric layer, wherein a remaining portion of the high-k gate dielectric is exposed. The remaining portion of the high-k gate dielectric layer is etched to provide a first high-k gate dielectric having a portion that extends beyond a sidewall of the first metal gate electrode and a second high-k gate dielectric having an edge that is aligned to a sidewall of the second metal gate electrode.

FIELD OF THE INVENTION

The present invention in one embodiment relates to semiconductorstructures having high-k gate dielectrics and gate electrodes composedof a metal.

BACKGROUND OF THE INVENTION

Programmable memory is being widely used in various electronicapplications, such as one-time programmable fuses, field-programmablegate array (FPGA) devices, and programmable logic arrays (PLA). Onecommonly used programmable memory type is a metal oxide semiconductorfield effect transistor (MOSFET) based on hot-carrier effects, in whicha high electrical field in the channel of the MOSFET generates hotcarriers, which produce electron-hole pairs through impact ionization.Electrons are injected and trapped in the spacer and holes are collectedby the substrate. Depending on whether electrons are trapped in thespacer or not, a logic value of “0” or “1” is produced.

SUMMARY OF THE INVENTION

A method is provided for integrating programmable memory MOSFETs withlogic MOSFETs. Broadly, the method includes providing a semiconductorsubstrate including a first portion and a second portion; forming alayered gate stack overlying the semiconductor substrate, the layeredgate stack including a high-k gate dielectric layer overlying thesemiconductor substrate and a metal electrode layer overlying the high-kgate dielectric layer; patterning the metal electrode layer stopping onthe high-k gate dielectric layer to provide a first metal gate electrodepresent in the first portion of the semiconductor substrate, and asecond metal gate electrode present in the second portion of thesemiconductor substrate; forming a spacer on the first metal gateelectrode overlying a portion of the high-k gate dielectric layer,wherein a remaining portion of the high-k gate dielectric that is notunderlying the first metal gate electrode, the second metal gateelectrode, and the portion of the high-k gate dielectric that isunderlying the spacer is exposed; and etching the remaining portion ofthe high-k gate dielectric layer to provide a first high-k gatedielectric having a portion that extends beyond a sidewall of the firstmetal gate electrode and a second high-k gate dielectric having an edgethat is aligned to a sidewall of the second metal gate electrode.

In another aspect, a memory device is provided that includesprogrammable memory MOSFETs and conventional MOSFETs. Broadly, thememory device includes a semiconductor substrate including a firstportion and a second portion; a programmable memory device present inthe first portion of the semiconductor substrate including a first gatestructure and spacers abutting the first gate structure, the first gatestructure including a first metal gate electrode overlying a firsthigh-k gate dielectric, wherein a portion of the first high-k gatedielectric is present underlying the spacers; and a semiconductor devicepresent in the second portion of the semiconductor substrate, thesemiconductor device including a second gate structure, the second gatestructure including a second metal gate electrode overlying a secondhigh-k gate dielectric, wherein a sidewall of the second metal gateelectrode is aligned to an edge of the second high-k gate dielectric.

In another aspect, a memory device is provided that includes a gatestructure and spacers abutting the gate structure, the gate structureincluding a metal gate electrode overlying a high-k gate dielectric,wherein a portion of the high-k gate dielectric is present underlyingthe spacers abutting the gate structure.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description, given by way of example and notintended to limit the invention solely thereto, will best be appreciatedin conjunction with the accompanying drawings, wherein like referencenumerals denote like elements and parts, in which:

FIG. 1 is a side cross-sectional view of a memory device, in accordancewith one embodiment of the present invention.

FIG. 2 is a side cross-sectional view of an initial structure includinga layered gate stack overlying a semiconductor substrate, the layeredgate stack including a high-k gate dielectric layer overlying thesemiconductor substrate and a metal electrode layer overlying the high-kgate dielectric layer.

FIG. 3 is a side cross-sectional view of patterning the metal electrodelayer stopping on the high-k gate dielectric layer to provide a firstmetal gate electrode present in the first portion of the semiconductorsubstrate and a second metal gate electrode present in the secondportion of the semiconductor substrate.

FIG. 4 is a side cross-sectional view depicting forming extension sourceand drain regions in the first portion and the second portion of thesemiconductor substrate.

FIG. 5 is a side cross-sectional view depicting forming a firstsacrificial spacer on the first metal gate electrode and a secondsacrificial spacer on the second metal gate electrode.

FIG. 6 is a side cross-sectional view depicting removing the secondsacrificial spacer from the second metal gate electrode, wherein aremaining portion of the high-k gate dielectric that is not underlyingthe first metal gate electrode, the second metal gate electrode, and theportion of the high-k gate dielectric that is underlying the firstsacrificial spacer is exposed.

FIG. 7 is a side cross-sectional view depicting etching the remainingportion of the high-k gate dielectric layer to provide a first high-kgate dielectric having a portion that extends beyond a sidewall of thefirst metal gate electrode and a second high-k gate dielectric having anedge that is aligned to a sidewall of the second metal gate electrode.

FIG. 8 is a side cross-sectional view depicting forming offset spacersabutting the first metal gate electrode and the second metal gateelectrode and forming deep source and drain regions in the first portionand the second portion of the semiconductor substrate.

FIGS. 9-12 depict another embodiment of the present invention thatbegins with the structure depicted in FIG. 3, wherein FIG. 9 depictsforming a first sacrificial spacer on the first metal gate electrode anda second sacrificial spacer on the second metal gate electrode.

FIG. 10 depicts removing the second sacrificial spacer from the secondmetal gate electrode, and performing the etching of the remainingportion of the high-k gate dielectric layer to provide a first high-kgate dielectric having the portion that extends beyond the sidewall ofthe first metal gate electrode and the second high-k gate dielectrichaving the edge that is aligned to the sidewall of the second metal gateelectrode.

FIG. 11 is a side cross-sectional view depicting forming extensionsource and drain regions in the first portion and the second portion ofthe semiconductor substrate.

FIG. 12 is a side-cross sectional view depicting forming offset spacersabutting the first metal gate electrode and the second metal gateelectrode; and forming deep source and drain regions in the firstportion and the second portion of the semiconductor substrate.

The above drawings represent some embodiments of the present invention,which are provided for illustrative purposes only are not intended tolimit the scope of the invention solely thereto.

DETAILED DESCRIPTION OF THE INVENTION

Detailed embodiments of the present invention are disclosed herein;however, it is to be understood that the disclosed embodiments aremerely illustrative of the invention that may be embodied in variousforms. In addition, each of the examples given in connection with thevarious embodiments of the invention are intended to be illustrative,and not restrictive. Further, the figures are not necessarily to scale,some features may be exaggerated to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the present invention.

The embodiments of the present invention relate to novel methods andstructures relating to gate structures in semiconductor and memorydevices. When describing the inventive methods and structures, thefollowing terms have the following meanings, unless otherwise indicated.

As used herein, “semiconductor device” refers to an intrinsicsemiconductor material that has been doped, that is, into which a dopingagent has been introduced, giving it different electrical propertiesthan the intrinsic semiconductor. Doping involves adding dopant atoms toan intrinsic semiconductor, which changes the electron and hole carrierconcentrations of the intrinsic semiconductor at thermal equilibrium.Dominant carrier concentrations in an extrinsic semiconductor classifyit as either an n-type or p-type semiconductor.

As used herein, the term “memory device” means a structure in which theelectrical state thereof can be altered and then retained in the alteredstate; in this way a bit of information can be stored.

As used herein a “field effect transistor” is a transistor in whichoutput current, i.e., source-drain current, is controlled by the voltageapplied to a gate structure. A field effect transistor has threeterminals, i.e., gate structure, source region and drain region.

As used herein, the term “device channel” is the region underlying thegate structure and between the source region and drain region thatbecomes conductive when the semiconductor device is turned on.

As used herein, the term “drain region” means a doped region in asemiconductor device located at the end of the device channel from whichcarriers are flowing out of the semiconductor device through the drainregion.

As used herein, the term “source region” is a doped region in asemiconductor device from which majority carriers are flowing into thedevice channel.

A “gate structure” means a structure used to control output current(i.e., flow of carriers in the channel) of a semiconductor device, suchas a field effect transistor (FET).

As used herein, the term “gate electrode” denotes a material having aconductivity ranging from 0.1Ω/square to 500Ω/square, which ispositioned overlying a gate dielectric.

As used herein, a “gate dielectric” is a layer of an insulator betweenthe semiconductor substrate and the gate electrode. (use very thinmetal, so we typically see 300 ohms/sq).

As used herein, “high k” denotes a dielectric material featuring adielectric constant (k) higher than about 3.9.

As used herein, a “metal” is an electrically conductive material, inwhich the metal atoms are held together by the force of a metallic bond,and the energy band structure of the metal's conduction and valencebands overlap, and hence, there is no energy gap.

As used herein, the term “selective” in reference to a material removalprocesses denotes that the rate of material removal for a first materialis greater than the rate of at least another material of the structureto which the material removal process is being applied. In oneembodiment, selective etching denotes an etch selectivity of 2:1 orgreater.

As used herein, “dopant regions” refers to portions of an intrinsicsemiconductor material in which the electrical conductivity of thematerial is dependent upon n-type or p-type dopants.

The term “anisotropic” denotes a material removal process in which thematerial removal rate in the direction normal to the surface of thematerial to which the etching species is being applied is greater thanin the direction parallel to the surface of the material to be removed.

As used herein, “insulating” or “dielectric” denotes a material having aroom temperature conductivity of less than about 10⁻¹⁰ (Ω-m)⁻¹.

The terms “direct physical contact” or “abutting” mean that the twostructures are in contact without any intermediary conducting,insulating or semiconducting structures.

The terms “overlying”, “underlying”, “atop”, and “on” define astructural relationship in which two structures are in contact where anintermediary structure of a conducting, insulating, or semiconductingmaterial may or may not be present at the interface of the twostructures.

For purposes of the description hereinafter, the terms “upper”, “lower”,“right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, andderivatives thereof shall relate to the invention, as it is oriented inthe drawing figures.

References in the specification to “one embodiment”, “an embodiment”,“an example embodiment”, etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

A variety of applications, such as system-on-chip, require formingprogrammable memory MOSFETs and logic MOSFETs, i.e., MOSFETs notconfigured for memory applications, on the same chip. However, aprogrammable memory field effect transistor (FET) and a logic MOSFEThave different and often competing requirements. For example, inprogrammable memory MOSFETs, it is desired to enhance charge trappingand thus to improve the program efficiency. In contrast, in logicMOSFETs, it is desired to suppress the charge trapping and thus tominimize shift of device characteristics.

In one embodiment, the present invention provides methods and structuresfor forming a high-k metal gate programmable memory metal oxidesemiconductor field effect transistor (MOSFET), and a semiconductordevice, such as a logic MOSFET, on the same semiconductor substrate. Theprogrammable memory MOSFET may be configured to enhance the efficiencyof electron trapping in the spacer of the device, and the semiconductordevice may be configured to reduce hot carrier effects.

FIG. 1 depicts one embodiment of a memory device, in accordance with thepresent invention. The memory device may include a semiconductorsubstrate 5 including a first portion 15 and a second portion 20, inwhich a programmable memory device 105 is present in the first portion15 and a semiconductor device 110 is present in the second portion 20.The programmable memory device 105 may include a first gate structure 35and at least one spacer 55 abutting the first gate structure 35. Thefirst gate structure 35 may include a first metal gate electrode 16overlying a first high-k gate dielectric 17, wherein a portion 30 of thefirst high-k gate dielectric 17 is present underlying the at least onespacer 55 abutting the first gate structure 35. The semiconductor device110 may include a second gate structure 40 composed of a second metalgate electrode 21 overlying a second high-k gate dielectric 22, whereina sidewall S₂ of the second metal gate electrode 21 is aligned to anedge 23 of the second high-k gate dielectric 22.

In one embodiment, the portion 30 of the first high-k gate dielectric 17that is present underlying the at least one spacer 55 abutting the firstgate structure 35 facilitates electron and hole trapping in the memoryfunction of the programmable memory device 105, and the sidewall S₂ ofthe second metal gate electrode 21 that is aligned to the edge 23 of thesecond high-k gate dielectric 22 reduces hot carrier effects in thesemiconductor device 110.

The first gate structure 35 may further include a first polysiliconlayer 14 a overlying the first metal gate electrode 16, and the secondgate structure 40 may further include a second polysilicon layer 14 boverlying the second metal gate electrode 21. In some embodiments, thepolysilicon layers 14 a and 14 b are omitted. The programmable memorydevice 105 and the semiconductor device 110 may further includeextension source and drain regions 7 and deep source and drain regions60, as depicted in FIG. 1. The above described memory device and themethods for forming memory devices are now described in greater detailreferring to FIGS. 2-12.

FIG. 2 depicts an initial structure for use in one embodiment of thepresent invention. The initial structure may include a layered gatestack 10 overlying a semiconductor substrate 5. The layered gate stack10 may include a high-k gate dielectric layer 12 overlying thesemiconductor substrate 5 and a metal electrode layer 13 overlying thehigh-k gate dielectric layer 12. Typically, the layered gate stack 10further includes a polysilicon layer 14 overlying the metal electrodelayer 13.

The semiconductor substrate 5 may include, but is not limited to: anysemiconducting material such conventional Si-containing materials,Germanium-containing materials, GaAs, InAs and other likesemiconductors. Si-containing materials include, but are not limited to:Si, bulk Si, single crystal Si, polycrystalline Si, SiGe, amorphous Si,silicon-on-insulator substrates (SOI), SiGe-on-insulator (SGOI),annealed poly Si, and poly Si line structures. When the semiconductorsubstrate 5 is a silicon-on-insulator (SOI) or SiGe-on-insulator (SGOI)substrate, the thickness of the Si-containing layer atop the buriedinsulating layer can have a thickness on the order of 30 nm or greater.The SOI or SGOI substrate may be fabricated using techniques that arewell known to those skilled in the art. For example, the SOI or SGOIsubstrate may be fabricated using a thermal bonding process, oralternatively be fabricated by an ion implantation process, which isreferred to in the art as separation by ion implantation of oxygen(SIMOX).

An isolation region 6 may be formed in the semiconductor substrate 5,wherein the isolation region 6 separates a first portion 15 of thesemiconductor substrate 5 from a second portion 20 of the semiconductorsubstrate 5. The isolation region 6 may be a shallow trench isolation(STI). The STI regions may be formed by etching a trench in thesemiconductor substrate 5 utilizing a conventional dry etching process,such as reactive-ion etching (RIE) or plasma etching. The trenches mayoptionally be lined with a conventional liner material, e.g., an oxide,and then chemical vapor deposition (CVD) or another like depositionprocess is used to fill the trench with polysilicon or another like STIdielectric material such as oxide and/or nitride. The STI dielectric mayoptionally be densified after deposition. A conventional planarizationprocess, such as chemical-mechanical polishing (CMP), may optionally beused to provide a planar structure. In some embodiments, the isolationregion is a LOCOS (Local Oxidation of Silicon) region formed by aconventional local oxidation of silicon process

Still referring to FIG. 2, the high-k gate dielectric layer 12 is formedatop the semiconductor substrate 5, and is typically an oxide-containingmaterial and is generally greater than about 0.8 nm thick. The high-kgate dielectric layer 12 is more typically from 1.0 nm to 2.0 nm thick,although lesser and greater thickness are also contemplated herein.

The high-k gate dielectric layer 12 may be a single layer or moretypically include multiple layers of materials. For example, the high-kgate dielectric layer 12 may include an interfacial layer (typicallysilicon oxide, silicon nitride, or silicon oxynitride) and a high-kmaterial with a dielectric constant greater than 7. The high-k gatedielectric layer 12 may also be composed of one or more materials,including but not limited to, silicon oxide, silicon nitride, siliconoxynitride, metal oxides such as hafnium oxide, hafnium silicon oxide,hafnium silicon oxynitride, lanthanum oxide, lanthanum aluminum oxide,zirconium oxide, zirconium silicon oxide, zirconium silicon oxynitride,tantalum oxide, titanium oxide, barium strontium titanium oxide, bariumtitanium oxide, strontium titanium oxide, yttrium oxide, aluminum oxide,lead scandium tantalum oxide, and lead zinc niobate, an any combinationof these materials.

The high-k gate dielectric layer 12 may be formed using depositiontechniques including, but not limited to: chemical vapor deposition(CVD), atomic layer CVD (ALCVD), pulsed CVD, plasma assisted CVD,sputtering, and chemical solution deposition. In another example, thehigh-k gate dielectric layer 12 further includes an interfacial layer,which may be formed by oxidation, oxynitridation, nitridation, chemicaloxidation, and/or plasma or radical treatment. It is noted that thehigh-k gate dielectric layer 12 is subsequently etched to form the firsthigh-k gate dielectric of the first gate structure and the second high-kgate dielectric of the second gate structure.

The metal electrode layer 13 is formed atop the high-k gate dielectriclayer 12 utilizing a deposition process, such as CVD, plasma-assistedCVD, plating, and/or sputtering, followed by planarization. The metalelectrode layer 13 may include any conductive metal including, but notlimited to: W, Ni, Ti, Mo, Ta, Cu, Pt, Ag, Au, Ru, Ir, Rh, and Re, andalloys that include at least one of the aforementioned conductiveelemental metals. When a combination of conductive elements is employed,an optional diffusion barrier material (not shown in the drawing) suchas TaN or WN may be formed between the conductive materials. The metalelectrode layer 13 may have a thickness T₁ ranging from 5 nm to 50 nm.More typically, the thickness T₁ of the metal electrode layer 13 rangesfrom 7.5 nm to 20 nm. It is noted that the metal electrode layer 13 issubsequently etched to form the first metal gate electrode of the firstgate structure and the second metal gate electrode of the second gatestructure.

Still referring to FIG. 2, the polysilicon layer 14 may be deposited bychemical vapor deposition (CVD). The polysilicon layer 14 can be dopedwith elements from group III-A or group V of the Periodic Table ofElements. The dopants may be introduced during deposition of thepolysilicon layer 14 or following subsequent formation of the gatestructure 10. The polysilicon layer 14 may have a thickness T₂ rangingfrom 20 nm to 200 nm. More typically, the thickness T₂ of thepolysilicon layer 14 ranges from 40 nm to 80 nm. It is again emphasizedthat in some embodiments of the present invention the polysilicon layer14 may be omitted. It is noted that the polysilicon layer 14 issubsequently etched to form the first polysilicon layer of the firstgate structure and the second polysilicon layer of the second gatestructure.

FIG. 3 depicts patterning the polysilicon layer (when present) andpatterning the metal electrode layer stopping on the high-k gatedielectric layer 12 to provide a first metal gate electrode 16 presentin the first portion 15 of the semiconductor substrate 20 and a secondmetal gate electrode 21 present in the second portion 20 of thesemiconductor substrate 5. The first metal gate electrode 16 and thesecond metal gate electrode 21 are formed utilizing photolithography andetch process steps. Specifically, a pattern is produced by applying amasking layer (photoresist or photoresist with an underlying hardmask)to the surface to be etched; exposing the photoresist to a pattern ofradiation; and then developing the pattern into the photoresistutilizing a resist developer. Once the patterning of the photoresist iscompleted, the sections covered by the photoresist are protected whilethe exposed regions are removed using a selective etching process thatremoves the unprotected regions. In one embodiment, the polysiliconlayer is etched and then utilized as an etch mask during the etchprocess that provides the first metal gate electrode 16 and the secondmetal gate electrode 21. It is noted that the above-described etchprocess may be utilized to provide the first polysilicon layer 14 a andthe second polysilicon layer 14 b, in the embodiments of the inventionin which the first polysilicon layer 14 a is present in the first gatestructure 35 and the second polysilicon layer 14 b is present in thesecond gate structure 40.

FIG. 4 depicts forming extension source and drain regions 7 in the firstportion 15 and the second portion 20 of the semiconductor substrate 5.The extension source and drain regions 7 may be formed by ionimplantation of n-type or p-type dopants into the semiconductorsubstrate 5. PFET devices are produced within Si-containingsemiconductor substrates by doping the source and drain extensionregions 7 with elements from group V of the Periodic Table of Elements.NFET devices are produced within Si-containing semiconductor substratesby doping the source and drain extension regions 7 with elements fromgroup V-A of the Periodic Table of Elements. In one example, the dopantfor the extension source and drain regions 7 includes arsenic (As), inwhich the arsenic is implanted at an energy ranging from 2 keV to 50keV, and the implant concentration ranges from 5×10¹³ atoms/cm² to1×10¹⁵ atoms/cm². Halo regions (not shown) can also be formed beneaththe source and drain extension regions 7 using an angled ionimplantation and a dopant having a conductivity type opposite the sourceand drain extension regions 7. Optionally, an extension offset spacer,which may include nitride and is not shown, may be formed before formingthe extension source and drain regions 7. The extension offset spacer,when present, may be removed after forming the extension source anddrain regions 7.

FIG. 5 depicts a first sacrificial spacer 9 on the sidewall of the firstgate structure 35 including the first metal gate electrode 16 and asecond sacrificial spacer 11 on the sidewall of the second gatestructure 40 of the second metal gate electrode 21. The firstsacrificial spacer 9 and the second sacrificial spacer 11 may becomposed of a dielectric material, such as an oxide, nitride, oxynitrideor combination thereof. Typically, the first sacrificial spacer 9 andthe second sacrificial spacer 11 are composed of a nitride, such assilicon nitride. The first sacrificial spacer 9 and the secondsacrificial spacer 11 may be provided by forming processes, such asdeposition or thermal growth. For example, the first sacrificial spacer9 and the second sacrificial spacer 11 may be formed by depositionprocesses, such as chemical vapor deposition (CVD) in combination withan anisotropic etch, such as reactive ion etch. The first sacrificialspacer 9 and the second sacrificial spacer 11 may each have a width W₁that typically ranges from 5 nm to 60 nm, although lesser and greaterthickness have also been contemplated herein. More typically, the firstsacrificial spacer 9 and the second sacrificial spacer 11 may each havea width W₁ that ranges from 10 nm to 20 nm.

FIG. 6 depicts removing the second sacrificial spacer 11 from the secondgate structure 40, wherein a remaining portion 12 a of the high-k gatedielectric layer 12 that is not underlying the first metal gateelectrode 16, the second metal gate electrode 21, and the portion of thehigh-k gate dielectric layer 12 that is underlying the first sacrificialspacer 9 is exposed. In one embodiment, the exposed portion, i.e.,remaining portion 12 a, of the high-k gate dielectric layer 12, isselected by forming an etch mask 25 overlying and protecting the firstportion 15 of the semiconductor substrate 5, in which the first gatestructure 30 including the first metal gate electrode 16 and the firstsacrificial spacer 9 is present, wherein the etch mask 25 is notoverlying the portion of the dielectric layer 12 that is present in thesecond portion 20. Further, as depicted in FIG. 6, the remaining portion12 a of the first dielectric layer 12 that is exposed is not presentunderlying the second metal gate conductor 21.

In one embodiment, an etch mask 25 is formed overlying the first portion15 of the semiconductor substrate 5. In one embodiment, the etch mask 25is a hardmask that is formed using deposition, photolithography, andhighly selective etching. In one example, a hardmask layer is firstdeposited overlying the first portion 15 and the second portion 20 ofthe semiconductor substrate 5. The hardmask layer may include dielectricsystems that can be deposited by chemical vapor deposition (CVD) andrelated methods. Typically, hardmask compositions include siliconoxides, silicon carbides, silicon nitrides, silicon carbonitrides, etc.Spin-on dielectrics may also be utilized as the hardmask layer includingbut are not limited too: silsesquioxanes, siloxanes, and boron phosphatesilicate glass (BPSG).

The hardmask layer is then patterned using photolithography.Specifically, a pattern is produced by applying a photoresist to thesurface to be patterned by exposing the photoresist to a pattern ofradiation, wherein the pattern is then developed into the photoresistutilizing a resist developer. Once the patterning of the photoresist iscompleted, the sections covered by the photoresist are protected, whilethe exposed regions are removed using a selective etching process thatremoves the unprotected regions of the hardmask layer forming the etchmask 25.

In another example, a photoresist mask may be used instead of thehardmask for the etch mask 25. The photoresist mask may be provided byapplying a photoresist layer, exposing the photoresist to a pattern ofradiation, and developing the pattern into the photoresist utilizing aresist developer. Once the patterning of the photoresist is completed,the sections of the semiconductor substrate 5 covered by the remainingphotoresist are protected.

Following the formation of the etch mask 25, the second sacrificialspacer 11 is then removed by an etch process having high selectivity toremoving the material of the second sacrificial spacer 11 withoutsubstantially etching the etch mask 25, the second metal gate electrode21, or when present the second polysilicon layer 14 b that is positionedoverlying the second metal gate electrode 21, and the semiconductorsubstrate 5. Following the removal of the second sacrificial spacer 11,the etch mask 25 may be removed using an etch process, such as selectiveetching.

FIG. 7 depicts etching the remaining portion, i.e., exposed portion, ofthe high-k gate dielectric layer after removing the etch mask to providea first high-k gate dielectric 17 having a portion 30 that extendsbeyond a sidewall S₁ of the first metal gate electrode 16 and a secondhigh-k gate dielectric 22 having an edge 23 that is aligned to asidewall S₂ of the second metal gate electrode 21. The term “aligned” asused to describe the relationship between the edge 23 of the secondhigh-k gate dielectric 22 and the sidewall S₂ of the second metal gateelectrode 21 means that exterior face of the edge 23 is coplanar, i.e,present on the same plane, with the exterior face of the sidewall S₂ ofthe second metal gate electrode 21. More specifically, in oneembodiment, the exterior face of the edge 23 and the exterior face ofthe sidewall S₂ are both present on a plane that is substantiallyperpendicular to the plane that is parallel to the upper surface of thesemiconductor substrate 5.

The remaining portion, i.e., exposed portion, of the high-k gatedielectric layer may be removed by an etch process, such as ananisotropic etch process, e.g., reactive ion etch (RIE). In oneembodiment, the etch process is a selective etch process, wherein theetch chemistry removes the material of the high-k gate dielectric layerselective to the semiconductor substrate 5, the first gate structure 35,the second gate structure 40, and the first sacrificial spacer 9.

The portion 30 of the first high-k gate dielectric 17 that is presentunderlying the first sacrificial spacer 9 abutting the first gatestructure 35 has a length L1 ranging from 2 nm to 40 nm, as measuredfrom the sidewall of the first metal gate electrode 16. More typically,the portion of the first high-k gate dielectric 17 that is presentunderlying the first sacrificial spacer 9 has a length L1 ranging from 5nm to 20 nm, as measured from the sidewall of the first metal gateelectrode 16.

FIG. 8 depicts forming a deep source and drain offset spacer 55 abuttingthe first gate structure 35 and the second gate structure 40, andforming deep source and drain regions 60 in the first portion 15 and thesecond portion 20 of the semiconductor substrate 5. In one embodiment,prior to forming the deep source and drain spacer 55, the firstsacrificial spacer 9 is removed from the first gate structure 35 usingan etch process. Similar to the first and second sacrificial spacers 9,11, the deep source and drain spacer 55 may be composed of a dielectricmaterial. The deep source and drain spacer 55 is typically composed of anitride or a combination of oxide and nitride materials. In one example,the deep source and drain spacer 55 includes a nitride, such as Si₃N₄.The deep source and drain spacer 55 may be formed using deposition andetch processes. The deep source and drain spacer 55 may have a spacerwidth W2 ranging from 10 nm to 60 nm, typically being about 15 nm.

Following deep source and drain spacer 55 formation, a higher energy ionimplant is conducted to form deep source and drain regions 60. Theseimplants are conducted at a higher energy and higher concentration ofdopant than the source and drain extension region 7 implant. The deepsource and drain regions 60 are typically doped with a dopant typeconsistent with the source and drain extension regions 7.

Following deep source and drain regions 60 formation, the source anddrain regions 60 are activated by activation annealing usingconventional processes such as, but not limited to: rapid thermalannealing, furnace annealing, flash-lamp annealing, laser annealing, orany combination of those processes. Activation anneal is conducted at atemperature ranging from 850° C. to 1350° C.

Still referring to FIG. 8, in one embodiment, the memory device of thepresent invention includes a programmable memory device 105 that ispresent in the first portion 15 of the semiconductor substrate 5 and asemiconductor device 110 that is present in the second portion 20 of thesemiconductor substrate 5.

In one embodiment, the programmable memory device 105 is a hot carriermemory field effect transistor (FET). The programmable memory device 105may include a first gate structure 35 and at least one spacer, i.e. deepsource and drain offset spacer 55, abutting the first gate structure 35,in which the first gate structure 35 includes the first metal gateelectrode 16 overlying a first high-k gate dielectric 17, wherein aportion 30 of the first high-k gate dielectric 17 is present underlyingthe spacer 55 abutting the first gate structure 35. As depicted in FIG.8, the first gate structure 35 may also include a first polysiliconlayer 14 a overlying the first metal gate electrode 16. In oneembodiment, the portion 30 of the first high-k gate dielectric 17 thatis present under the deep source and drain offset spacer 55 of the hotcarrier memory FET i.e., programmable memory device 105, enhances theefficiency of trapping electrons in the deep source and drain offsetspacer 55 due to the lower electron injection barrier of the high-k gatedielectric, i.e., first high-k gate dielectric 17, than the siliconoxide (SiO₂) or the silicon nitride (Si₃N₄) spacer 55. As discussedabove, the dielectric material of the first high-k gate dielectric 17may be composed of at least one of HfO₂, ZrO₂, Al₂O₃, TiO₂, La₂O₃,SrTiO₃, LaAlO₃, and Y₂O₃. In one example, in which the first high-k gatedielectric 17 of the programmable memory device 105 is composed of HfO₂,the barrier is approximately 1.5 eV, as compared to 3.5 eV for a similardevice in which the gate dielectric is composed of SiO₂.

In one embodiment, the semiconductor device 110 includes a second gatestructure 40 having a second metal gate electrode 21 overlying a secondhigh-k gate dielectric 22, wherein a sidewall S₂ of the second metalgate electrode 21 is aligned to an edge 23 of the second high-k gatedielectric 22. The semiconductor device 110 may be a logic device, whichtypically performs a logic function instead of a memory function by amemory device. In one embodiment, the above described semiconductordevice 110, and method of forming thereof, produces a reduced hotcarrier effect by not incorporating a high-k dielectric materialunderlying the offset spacer 55 that abuts the gate structure, i.e., thesecond gate structure 40, of the semiconductor device.

FIGS. 9-12 depict another embodiment of a method for forming a memorydevice, as depicted in FIG. 1, wherein FIG. 9 depicts forming a firstsacrificial spacer 9 on the first metal gate electrode 16 and a secondsacrificial spacer 11 on the second metal gate electrode 21 of thestructure depicted in FIG. 3. The description of forming the firstsacrificial spacer 9 and the second sacrificial spacer 11 describedabove with reference to FIG. 5 is applicable to the embodiment of theinvention depicted in FIG. 9.

FIG. 10 depicts removing the second sacrificial spacer from the secondmetal gate electrode 21, and etching an exposed portion of the high-kgate dielectric layer. Similar to the embodiment described above, theetch step provides a first gate structure 35 including a first high-kgate dielectric 17 having a portion 30 that extends beyond the sidewallS₁ of the first metal gate electrode 16 and a second gate structure 40that includes the second high-k gate dielectric 22 having the edge 23that is aligned to the sidewall S₂ of the second metal gate electrode21.

Referring now to FIG. 11, in a next process step, the extension sourceand drain regions 7 are formed in the first portion 15 and the secondportion 20 of the semiconductor substrate 5. Deep source and drainoffset spacers 55 are then formed abutting the first metal gateelectrode 16 and the second metal gate electrode 21, and deep source anddrain regions 60 are formed in the first portion 15 and the secondportion 20 of the semiconductor substrate 5, as depicted in FIG. 12.

While the present invention has been particularly shown and describedwith respect to preferred embodiments thereof, it will be understood bythose skilled in the art that the foregoing and other changes in formsand details may be made without departing from the spirit and scope ofthe present invention. It is therefore intended that the presentinvention not be limited to the exact forms and details described andillustrated, but fall within the scope of the appended claims.

1. A method of forming a memory device comprising: providing asemiconductor substrate comprising a first portion and a second portion;forming a layered gate stack overlying the semiconductor substrate, thelayered gate stack comprising a high-k gate dielectric layer overlyingthe semiconductor substrate and a metal electrode layer overlying thehigh-k gate dielectric layer; patterning the metal electrode layerstopping on the high-k gate dielectric layer to provide a first metalgate electrode present in the first portion of the semiconductorsubstrate, and a second metal gate electrode present in the secondportion of the semiconductor substrate; forming at least one spacer onthe first metal gate electrode overlying a portion of the high-k gatedielectric layer, wherein a remaining portion of the high-k gatedielectric that is not underlying the first metal gate electrode, thesecond metal gate electrode, and the portion of the high-k gatedielectric that is underlying the at least one spacer is exposed; andetching the remaining portion of the high-k gate dielectric layer toprovide a first high-k gate dielectric having a portion that extendsbeyond a sidewall of the first metal gate electrode and a second high-kgate dielectric having an edge that is aligned to a sidewall of thesecond metal gate electrode.
 2. The method of claim 1, wherein thesemiconductor substrate is a semiconductor on insulator (SOI) substrateor is a bulk semiconductor substrate.
 3. The method of claim 1, whereinthe first portion of the semiconductor substrate is separated from thesecond portion of the semiconductor substrate by an isolation region. 4.The method of claim 1, wherein the forming of the layered gate stackfurther comprises a polysilicon layer overlying the metal electrodelayer.
 5. The method of claim 1, wherein forming the at least one spacercomprises depositing a dielectric material, and anisotropically etchingthe dielectric material.
 6. The method of claim 1 further comprisingforming extension source and drain regions in the first portion and thesecond portion of the semiconductor substrate following the formation ofthe first metal gate electrode and the second metal gate electrode. 7.The method of claim 6, wherein the forming of the at least one spacer onthe first metal gate electrode overlying the portion of the high-k gatedielectric layer comprises forming a first sacrificial spacer on thefirst metal gate electrode and a second sacrificial spacer on the secondmetal gate electrode; and removing the second sacrificial spacer fromthe second metal gate electrode, wherein the first sacrificial spacer onthe first metal gate electrode provides the at least one spacer.
 8. Themethod of claim 7, further comprising removing the first sacrificialspacer from the first metal gate electrode.
 9. The method of claim 8,further comprising forming offset spacers abutting the first metal gateelectrode and the second metal gate electrode and forming deep sourceand drain regions in the first portion and the second portion of thesemiconductor substrate.
 10. The method of claim 7, further comprisesforming offset spacers abutting the first metal gate electrode and thesecond metal gate electrode; and forming deep source and drain regionsin the first portion and the second portion of the semiconductorsubstrate.
 11. The method of claim 1, wherein the portion of the firsthigh-k dielectric that extends beyond the sidewall of the first metalgate electrode ranges from 2 nm to 40 nm.
 12. The method of claim 1further comprising: forming a first sacrificial spacer on the firstmetal gate electrode and a second sacrificial spacer on the second metalgate electrode; removing the second sacrificial spacer from the secondmetal gate electrode; performing the etching of the remaining portion ofthe high-k gate dielectric layer to provide a first high-k gatedielectric having the portion that extends beyond the sidewall of thefirst metal gate electrode and the second high-k gate dielectric havingthe edge that is aligned to the sidewall of the second metal gateelectrode; removing the first sacrificial spacer from the first metalgate electrode; forming extension source and drain regions in the firstportion and the second portion of the semiconductor substrate; formingoffset spacers abutting the first metal gate electrode and the secondmetal gate electrode; and forming deep source and drain regions in thefirst portion and the second portion of the semiconductor substrate. 13.A memory device comprising: a semiconductor substrate including a firstportion and a second portion; a programmable memory device present inthe first portion of the semiconductor substrate comprising a first gatestructure and spacers abutting the first gate structure, the first gatestructure comprising a first metal gate electrode overlying a firsthigh-k gate dielectric, wherein a portion of the first high-k gatedielectric is present underlying the spacers abutting the first gatestructure; and a semiconductor device present in the second portion ofthe semiconductor substrate, the semiconductor device comprising asecond gate structure, the second gate structure comprising a secondmetal gate electrode overlying a second high-k gate dielectric, whereina sidewall of the second metal gate electrode is aligned to an edge ofthe second high-k gate dielectric.
 14. The memory device of claim 13,wherein first gate structure further comprises a first polysilicon layeroverlying the first metal gate electrode, and a second polysilicon layeroverlying the second metal gate electrode.
 15. The memory device ofclaim 13, wherein at least one of the first metal gate electrode and thesecond metal gate electrode is comprised of Co, Ni, Ti, W, Mo, Ta, TiN,TaC, WN, or a combination thereof.
 16. The memory device of claim 13,wherein at least one of the first high-k gate dielectric and the secondhigh-k gate dielectric is comprised of HfO₂, ZrO₂, Al₂O₃, TiO₂, La₂O₃,SrTiO₃, LaAlO₃, Y₂O₃ and mixtures thereof.
 17. The memory device ofclaim 13, wherein the portion of the first high-k gate dielectric thatis present underlying the spacers abutting the first gate structure hasa length ranging from 2 nm to 30 nm as measured from the sidewall of thefirst metal gate electrode.
 18. A memory device comprising: a gatestructure and spacers abutting the gate structure, the gate structurecomprising a metal gate electrode overlying a high-k gate dielectric,wherein a portion of the high-k gate dielectric is present underlyingthe spacers abutting the gate structure.
 19. The memory device of claim18, wherein the high-k gate dielectric is comprised of HfO₂, ZrO₂,Al₂O₃, TiO₂, La₂O₃, SrTiO₃, LaAlO₃, Y₂O₃ and mixtures thereof.
 20. Thememory device of claim 18, wherein the portion of the high-k gatedielectric that is present underlying the spacers abutting the gatestructure has a length ranging from 2 nm to 30 nm as measured from thesidewall of the metal gate electrode.